/**
 * md5 (message-digest algorithm) implemented source file.
 * 	@package src/cel_md5.c
 *
 * Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
 * rights reserved.
 * 
 * License to copy and use this software is granted provided that it
 * is identified as the "RSA Data Security, Inc. MD5 Message-Digest
 * Algorithm" in all material mentioning or referencing this software
 * or this function.
 * 
 * License is also granted to make and use derivative works provided
 * that such works are identified as "derived from the RSA Data
 * Security, Inc. MD5 Message-Digest Algorithm" in all material
 * mentioning or referencing the derived work.
 * 
 * RSA Data Security, Inc. makes no representations concerning either
 * the merchantability of this software or the suitability of this
 * software for any particular purpose. It is provided "as is"
 * without express or implied warranty of any kind.
 * These notices must be retained in any copies of any part of this
 * documentation and/or software.
 * 
 */
#include "cel_hash.h"
#include <stdlib.h>
#include <string.h>

//Constants for md5 transform.
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21

static uchar_t MD5_PADDING[64] = {
    0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

/*
 * F G H, I are basic md5 functions.
 */
#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))

//rotates x left n bits.
#define ROTATE_LEFT( x, n ) (((x) << (n))|((x) >> (32-(n))))

/* 
 * FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
 * Rotation is separate from addition to prevent recomputation.
 */
#define FF(a, b, c, d, x, s, ac) \
{ \
    (a) += F((b), (c), (d)) + (x) + (ulong_t)(ac); \
    (a) = ROTATE_LEFT((a), (s)); \
    (a) += (b); \
}
#define GG(a, b, c, d, x, s, ac) \
{ \
    (a) += G((b), (c), (d)) + (x) + (ulong_t)(ac); \
    (a) = ROTATE_LEFT((a), (s)); \
    (a) += (b); \
}
#define HH(a, b, c, d, x, s, ac) \
{ \
    (a) += H((b), (c), (d)) + (x) + (ulong_t)(ac); \
    (a) = ROTATE_LEFT ((a), (s)); \
    (a) += (b); \
}
#define II(a, b, c, d, x, s, ac) \
{ \
    (a) += I((b), (c), (d)) + (x) + (ulong_t)(ac); \
    (a) = ROTATE_LEFT((a), (s)); \
    (a) += (b); \
}

static void md5_transform( ulong_t state[4], uchar_t block[64] );
static void Encode( uchar_t * output, ulong_t * input, uint_t len );
static void Decode( ulong_t * output, uchar_t * input, uint_t len );

/*
 * md5 initialization.
 */
CEL_API void cel_md5_init( cel_md5_t context )
{
    context->count[0] = context->count[1] = 0;

    //load magic initialize constants.
    context->state[0] = 0x67452301;
    context->state[1] = 0xefcdab89;
    context->state[2] = 0x98badcfe;
    context->state[3] = 0x10325476;
}

/*
 * md5 block update operation.
 * 	continue an md5 message-digest operation, processing
 * 	another message block and update the context.
 *
 * @param	input	- the block.
 * @param	length	- the length of the input in bytes.
 */
CEL_API void cel_md5_update( 
	cel_md5_t context, uchar_t * input, uint_t inputLen )
{
    uint_t i, index, partLen;

    /* Compute number of bytes mod 64 */
    index = (uint_t)((context->count[0] >> 3) & 0x3F);

    /* Update number of bits */
    if ((context->count[0] += ((ulong_t)inputLen << 3)) 
	    < ((ulong_t)inputLen << 3))
	context->count[1]++;
    context->count[1] += ((ulong_t)inputLen >> 29);

    partLen = 64 - index;

    //Transform as many times as possible.
    if ( inputLen >= partLen ) 
    {
	//cel_mem_copy( input, &context->buffer[index], partLen );
	memcpy( &context->buffer[index], input, partLen );
	md5_transform( context->state, context->buffer );

	for ( i = partLen; i + 63 < inputLen; i += 64 )
	    md5_transform( context->state, &input[i] );

	index = 0;
    }
    else
	i = 0;

    /* Buffer remaining input */
    //cel_mem_copy( &input[i], &context->buffer[index], inputLen - i );
    memcpy( &context->buffer[index], &input[i], inputLen - i );
}

CEL_API void cel_md5_final( cel_md5_t context, uchar_t digest[16] )
{
    uchar_t bits[8];
    uint_t index, padlen;

    /* save number of bits */
    Encode( bits, context->count, 8UL );

    //pad out to 56 mod 64.
    index = (uint_t)( (context->count[0] >> 3) & 0x3f );
    padlen = (index < 56) ? (56 - index) : (120 - index);
    cel_md5_update( context, MD5_PADDING, padlen );

    /* append length (before padding) */
    cel_md5_update( context, bits, 8UL );

    /* store state in digest */
    Encode( digest, context->state, 16UL );

    //zeroize sensitive information.
    memset( context, 0x00, sizeof(*context) );
}

    static void 
md5_transform( ulong_t state[4], uchar_t block[64] )
{
    ulong_t a = state[0], b = state[1], c = state[2], d = state[3], x[16];

    Decode(x, block, 64);

    /* Round 1 */
    FF(a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
    FF(d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
    FF(c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
    FF(b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
    FF(a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
    FF(d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
    FF(c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
    FF(b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
    FF(a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
    FF(d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
    FF(c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
    FF(b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
    FF(a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
    FF(d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
    FF(c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
    FF(b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

    /*Round 2 */
    GG(a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
    GG(d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
    GG(c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
    GG(b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
    GG(a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
    GG(d, a, b, c, x[10], S22,  0x2441453); /* 22 */
    GG(c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
    GG(b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
    GG(a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
    GG(d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
    GG(c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
    GG(b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
    GG(a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
    GG(d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
    GG(c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
    GG(b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

    /*Round 3 */
    HH(a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
    HH(d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
    HH(c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
    HH(b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
    HH(a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
    HH(d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
    HH(c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
    HH(b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
    HH(a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
    HH(d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
    HH(c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
    HH(b, c, d, a, x[ 6], S34,  0x4881d05); /* 44 */
    HH(a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
    HH(d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
    HH(c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
    HH(b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */

    /*Round 4 */
    II(a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
    II(d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
    II(c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
    II(b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
    II(a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
    II(d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
    II(c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
    II(b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
    II(a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
    II(d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
    II(c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
    II(b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
    II(a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
    II(d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
    II(c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
    II(b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */

    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;

    /* 
     * Zeroize sensitive information.
     */
    memset( x, 0x00, sizeof(x) );
}

/* 
 * Encodes input (uint_t) into output (unsigned char). Assumes len is
 *   a multiple of 4.
 */
static void Encode( 
	uchar_t * output, ulong_t * input, uint_t len )
{
    uint_t i, j;

    for ( i = 0, j = 0; j < len; i++, j += 4 ) 
    {
	output[j  ] = (uchar_t)((input[i]     )  & 0xff);
	output[j+1] = (uchar_t)((input[i] >> 8)  & 0xff);
	output[j+2] = (uchar_t)((input[i] >> 16) & 0xff);
	output[j+3] = (uchar_t)((input[i] >> 24) & 0xff);
    }
}

/* 
 * Decodes input (unsigned char) into output (uint_t). Assumes len is
 *   a multiple of 4.
 */
static void Decode( 
	ulong_t * output, uchar_t * input, uint_t len )
{
    uint_t i, j;

    for ( i = 0, j = 0; j < len; i++, j += 4 )
    {
	output[i] = ((ulong_t)input[j]) 
	    | (((ulong_t)input[j+1]) << 8) 
	    | (((ulong_t)input[j+2]) << 16) 
	    | (((ulong_t)input[j+3]) << 24);
    }
}

/*
 * MD5 hash algorithm.
 * 	Message digest Algorithm 5.
 *
 * Digest a string and get the results.
 */
CEL_API void cel_md5_string( 
	const cstring str, uchar_t digest[16] )
{
    cel_md5_entry context;
    uint_t len = strlen( str );

    cel_md5_init( &context );
    cel_md5_update( &context, (uchar_t *) str, len );
    cel_md5_final( &context, digest );
}

/* Digest a file and get the result.
 * */
CEL_API int cel_md5_file( 
	const cstring filename, uchar_t digest[16] )
{
    cel_md5_entry context;
    FILE * file;
    int len;
    uchar_t buffer[1024];

    if ( ( file = fopen( filename, "rb" ) ) == NULL )
	return -1;
    else {
	cel_md5_init( &context );
	while ( (len = (int) fread( buffer, 1, 1024, file )) > 0 ) 
	    cel_md5_update( &context, buffer, len );
	cel_md5_final( &context, digest );

	//close the file
	fclose( file );
    }

    return 0;
}
